Microwatt fuel cell stack

Abstract

A microwatt fuel cell stack that demonstrates a wide range temperature tolerance, low reactant cross-over and leakage, low internal leakage current, and/or effective water transport is disclosed. Both H 2 and O 2 may be supplied directly to the fuel cell stack (i.e., dead-ended). One-piece gas diffusion electrodes (GDEs) may serve as both the active electrode and manifold port. Water removal may be accomplished by permeation through the membrane to “fins” exposed by notches in the bipolar plates and gaskets.

The invention claimed is: 
     
       1. A fuel cell stack, comprising:
 a plurality of fuel cells comprising a plurality of layers, the plurality of fuel cells each comprising:
 a membrane, 
 a first gasket on a side of the membrane, the first gasket comprising a first gas diffusion electrode (GDE) that, in operation, is provided with a hydrogen gas supply via a hydrogen manifold, and 
 a second gasket on an opposite side of the membrane with respect to the first gasket, the second gasket comprising a second GDE that, in operation, is provided with an oxygen gas supply via an oxygen manifold, wherein 
 
 a water permeability coefficient of the first gasket and the second gasket is greater than a gas permeability coefficient of the first gasket and the second gasket, 
 the membrane comprises a plurality of fins, and 
 the first gasket and the second gasket each comprise at least one notch such that at least one respective fin of the plurality of fins of the membrane is exposed by the at least one notch in the first gasket and the second gasket. 
 
     
     
       2. The fuel cell stack of  claim 1 , wherein
 each fuel cell of the plurality of fuel cells further comprises at least one bipolar plate with at least one notch matching the at least one notch of an adjacent one of the first gasket or the second gasket, and 
 each fuel cell shares a bipolar plate with a fuel cell directly above and below it, with the exception of a top cell that does not have a bipolar plate above the top fuel cell and a bottom cell that does not have a bipolar plate below the bottom fuel cell. 
 
     
     
       3. The fuel cell stack of  claim 2 , wherein
 the at least one bipolar plate comprises titanium that is nitrided, platinum-coated, or gold coated, 
 the membrane comprises a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer, and 
 the first GDE and the second GDE comprise platinum black. 
 
     
     
       4. The fuel cell stack of  claim 1 , wherein the first gasket and the second gasket are oriented in opposite directions with respect to one another such that the first GDE and the second GDE are properly oriented to interface with the hydrogen manifold or the oxygen manifold, respectively. 
     
     
       5. The fuel cell stack of  claim 1 , wherein the fuel cell stack is configured such that both hydrogen gas and oxygen gas are supplied directly to the fuel cell stack in a dead-ended configuration and air is not provided. 
     
     
       6. The fuel cell stack of  claim 1 , wherein the first GDE and the second GDE serve as both an active electrode and a manifold port for the hydrogen manifold and the oxygen manifold, respectively. 
     
     
       7. The fuel cell stack of  claim 1 , wherein each fuel cell comprises a barrier plate. 
     
     
       8. The fuel cell stack of  claim 1 , wherein each layer of each fuel cell comprises holes defining passageways for the hydrogen and oxygen manifolds, respectively. 
     
     
       9. The fuel cell stack of  claim 8 , wherein a bottom fuel cell of the plurality of fuel cells comprises an endplate that does not include holes for the hydrogen and oxygen manifolds. 
     
     
       10. The fuel cell stack of  claim 8 , wherein
 a bottom fuel cell of the plurality of fuel cells comprises an endplate comprising holes for the hydrogen and oxygen manifolds, 
 the fuel cell stack further comprises respective plugs and O-ring seals for each manifold hole of the endplate, and 
 the plugs are one or more orders of magnitude more permeable to water than gas to selectively remove water proximate to the plugs. 
 
     
     
       11. The fuel cell of  claim 1 , wherein
 the first GDE and the second GDE each comprise a tongue, a throat, and a head, and 
 in operation, gas flows from the tongue through the throat and on to the head. 
 
     
     
       12. The fuel cell stack of  claim 11 , wherein the throat of the first GDE and the second GDE is flush with, and has a same compressed thickness as, the first gasket and the second gasket, respectively. 
     
     
       13. The fuel cell stack of  claim 11 , wherein the tongue and the throat connect the head of the first GDE and the second GDE to the hydrogen manifold and the oxygen manifold, respectively. 
     
     
       14. A fuel cell, comprising:
 a membrane comprising a plurality of fins, 
 a first gasket on a side of the membrane, the first gasket comprising a first gas diffusion electrode (GDE) that, in operation, is provided with a hydrogen gas supply via a hydrogen manifold, and 
 a second gasket on an opposite side of the membrane with respect to the first gasket, the second gasket comprising a second GDE that, in operation, is provided with an oxygen gas supply via an oxygen manifold, wherein 
 the first gasket and the second gasket each comprise at least one notch such that respective membrane fins are exposed by the at least one notch in the first gasket and the second gasket, and 
 a water permeability coefficient of the first gasket and the second gasket is greater than a gas permeability coefficient of the first gasket and the second gasket. 
 
     
     
       15. The fuel cell of  claim 14 , further comprising:
 at least one bipolar plate with at least one notch matching the at least one notch of an adjacent one of the first gasket or the second gasket. 
 
     
     
       16. The fuel cell of  claim 14 , wherein
 the first gasket and the second gasket are oriented in opposite directions with respect to one another such that the first GDE and the second GDE are properly oriented to interface with the hydrogen manifold or the oxygen manifold, respectively, 
 the fuel cell stack is configured such that both hydrogen gas and oxygen gas are supplied directly to the fuel cell stack in a dead-ended configuration and air is not provided, and 
 the first GDE and the second GDE serve as both an active electrode and a manifold port for the hydrogen manifold and the oxygen manifold, respectively. 
 
     
     
       17. The fuel cell of  claim 14 , further comprising:
 holes defining passageways for the hydrogen and oxygen manifolds, respectively; 
 an endplate comprising holes for the hydrogen and oxygen manifolds; and 
 respective plugs and O-ring seals for each manifold hole of the endplate, wherein 
 the plugs are one or more orders of magnitude more permeable to water than gas to selectively remove water proximate to the plugs. 
 
     
     
       18. The fuel cell of  claim 14 , wherein
 the first GDE and the second GDE each comprise a tongue, a throat, and a head, 
 in operation, gas flows from the tongue through the throat and on to the head, 
 the throat of the first GDE and the second GDE is flush with, and has a same compressed thickness as, the first gasket and the second gasket, respectively, and 
 the tongue and the throat connect the head of the first GDE and the second GDE to the hydrogen manifold and the oxygen manifold, respectively. 
 
     
     
       19. A microwatt fuel cell, comprising:
 a membrane comprising a plurality of fins, 
 a first gasket on a side of the membrane, the first gasket comprising a first gas diffusion electrode (GDE) that, in operation, is provided with a hydrogen gas supply via a hydrogen manifold, and 
 a second gasket on an opposite side of the membrane with respect to the first gasket, the second gasket comprising a second GDE that, in operation, is provided with an oxygen gas supply via an oxygen manifold, wherein 
 the first GDE and the second GDE each comprise a tongue, a throat, and a head, 
 the tongue and the throat connect the head of the first GDE and the second GDE to the hydrogen manifold and the oxygen manifold, respectively, 
 a water permeability coefficient of the first gasket and the second gasket is greater than a gas permeability coefficient of the first gasket and the second gasket, and 
 the first gasket and the second gasket each comprise at least one notch such that at least one respective fin of the plurality of fins of the membrane is exposed by the at least one notch in the first gasket and the second gasket.